Analysis of Optimal Conditions of Hydrophobic Film Formation by Film-Forming Amines on Carbon Steel

Several types of fatty amine are referred to film-forming amines (FFAs), which form hydrophobic films on metal surfaces and are candidates of corrosion inhibitors for water circuits of power plants. In this study, the characteristics of hydrophobic films formed with various FFA and an amide were compared. Electrochemical quartz crystal microbalance measurements at 298 K revealed that a high-molecular-weight monoamine formed an organic film with a greater mass on an iron surface than a low-molecular-weight monoamine, a diamine, and an amide. It was shown that the organic film with a greater mass had higher hydrophobicity and film resistance by contact angle measurements between water droplet and carbon steel specimen immersed in advance in FFA-containing solution at 353 K and electrochemical impedance spectroscopy at 303 K. The consistency in the results of those three types of measurements indicates the relationship among the mass, hydrophobicity, and electrical resistance of the organic film. The electrical resistance of the film saturated with specimen exposure time to an FFA-containing solution, and the given film resistance per unit amount of FFA decreased with the concentration, suggesting that the efficiency of FFA to mitigate corrosion has an upper limit, and therefore, those film-treatment conditions can be optimized.